EFI people, what do you think?

Discussion in 'High Tech Retrofits' started by rocket dawg, Apr 8, 2018.

  1. rocket dawg

    rocket dawg Veteran Member

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    Holley responded to my email question saying the air gap rpm manifold will work fine.
     
  2. 73 Z

    73 Z Veteran Member Gold Member

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    Manifold pictured above is a Vic jr.
    Glad to hear the RPM works, I'm going with the Sniper as well
     
  3. rocket dawg

    rocket dawg Veteran Member

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    They say I need a fuel return line. I havent looked yet to see if I have one. I know I have a vent line going from the front of the car to the gas tank. Not sure if I could use that ( I doubt it) Is adding a return line an easy job? I'm not sure my stock fuel lines will hold 50 psi if I drop an in tank fuel pump in. So all new lines must be run?
     
  4. 8pack

    8pack Veteran Member Lifetime Gold Member

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    Yes you need a return line....you cannot use the vent line that goes down the drivers side of the car. It returns to a pin hole at the top of the tank and the gas cannot get through that hole fast enough. That is a vent or vapor line that used to connect up to the charcoal canister and was part of the emissions system pulling vapor out of the tank.... I took my tank apart to verify that.

    You can however use the fuel return line that goes down the passenger side of the car next to the supply line. That is what I am using as are many others. If you want you can run a larger dedicated line but it seems like a waste to me if you already have the return line there.....

    The supply line is running the high pressure....If that is metal (and it is not rusting through!) you are fine, you just need the right connectors to high pressure rubber line if that is what you use to get from the stock lines to the sniper.

    The return is low pressure.....3psi... I do know that when Holley suggests you check your fuel pressure they recommend a 0-100PSI gauge on the feed and a 0-15 on the return
     
    Last edited: May 11, 2018
  5. jvle95

    jvle95 Veteran Member

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    8pack,
    What size is your stock return line that you are using. I am just about ready to install a sniper on my 72 and was thinking of using the Holley filter/regulator set near the tank so I could use a short return line but my car does have a stock return line that I could possibly use as well. Everything I have read has said that the stock return line is too small?
     
  6. 8pack

    8pack Veteran Member Lifetime Gold Member

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    Danny Cabral seems to be the resident expert on the Sniper forum..........Image and link. I am running the stock Mechanical fuel pump up to a RobbMCC Power Surge tank....

    SUPPLY - 3/8" supply from the gas tank to mechanical pump to Power Surge to Sniper
    RETURN - 3/8" return from Sniper to the Power Surge, 5/16" from Power surge to the gas tank. All research I have done seems to say that the 5/16" return is acceptable....it is running 3psi...we must be reading different forums! I am sticking with what it says on the Holley Forum....

    READ THIS WHOLE THREAD....it answers all the fuel line questions.

    https://forums.holley.com/showthread.php?21343-Return-Line&p=94303#post94303

    upload_2018-5-11_13-23-41.png
     
    Last edited: May 11, 2018
  7. jvle95

    jvle95 Veteran Member

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    Appreciate the response. I have read that thread and I guess a better way to word my question is to ask, is your return line the stock line? I have read that the stock return lines are 5/16 ID and some have said 1/4 ID. Am I missing something? Did they change at some point?
     
  8. 8pack

    8pack Veteran Member Lifetime Gold Member

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    Mine is a '78 and I used the stock line....don't know the answer to the second part of the question. I believe the line size is determined by the OD of the steel line.....EDIT>>>> Now that I sit here thinking about it my feed from the tank to the mechanical pump might be 5/16" and the return 1/4"....I need to go measure again or someone on here can confirm stock sizes...However, my lines to and from the power surge tank to the Sniper are 3/8"/-6AN for sure...INLINE Tube shows 3/8" Supply, 1/4" Return as stock..

    Measuring standard....

    Tubing is OD X wall thickness
    Pipe is ID X schedule
    Hose is ID

    http://www.chevelles.com/forums/45-chevelle-tech/137478-how-tell-3-8-fuel-line-5-16-a.html
     
    Last edited: May 11, 2018
  9. BigBlock73

    BigBlock73 Veteran Member Lifetime Gold Member

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    I used the vent line for the return line from front to back and I used one of the other vent lines (vapor)going into the tank.
    I can hear the gas going into the tank.
     
  10. jvle95

    jvle95 Veteran Member

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    My car currently has both, a 3/8" supply and a return which I am not using now. I just measured the outer diameter and it looks to be a bit over 8mm which would make it 5/16" I think. It has been painted so I guess that would account for the slightly larger diameter. Weird thing is I can not find a solid answer that says it should be 5/16" vs 1/4". Looks like replacement items are 3/8" and 1/4" as mentioned by 8pack. The car is a 72 RS/SS if that makes a difference. Using that stock return line would really make the install easier. Didnt mean to get this thread off topic but just curious.
     

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